Relationship of convenience is a relationship between a man and a woman which isn't based on love; moreover, there is no mutual love existing in such relationship.
The notion of a relationship of convenience implies the fact that the key word is 'convenience', not 'relationship'.
What exactly does it mean? It means that two people - man and woman (typically traditionally) unite in a relationship just because it's convenient for them to be together.
When there are no feelings within the married couple or even if convenience is craved by one of the partners only and the other is blissfully ignorant of it, marriage starts weighing upon you like a heavy dark cloud almost since the very moment when you act out your wedding vows to each other. Such relationship makes a person weak, empty and apathetic.
